Line an 8x8-inch tin with baking paper.
Add the butter and mini marshmallows to a saucepan. Place over low heat and stir gently until melted.
Remove the pan from the heat and stir in the peppermint extract and food colouring.
Once you're happy with the colour, stir in the Rice Krispies.
Leave to cool for a few minutes then quickly stir in the chocolate chips.
Press the mixture into your lined tin with a metal spoon or silicone spatula. If the mixture is too sticky, wait a couple of minutes before trying again.
Top with a few more chocolate chips.
Leave to set for 1 hour, then remove it from the tin, cut it into squares and enjoy.